Anna Rubio

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Euskoos, the coastal observatory of the southeast Bay of Biscay, has been operational for over 15 years, collecting data on various physical variables in the region. Recent initiatives aim to develop an enhanced multidisciplinary observatory that can address critical needs related to the sustainable management of this coastal area and the challenges related to global change. Available observation infrastructures include a high-frequency radar system, a network of buoys, coastal and videometry stations, two gliders, and two autonomous surface vehicles equipped with biogeochemical and biological sensors. These technologies, combined with metocean models and satellite data, enable detailed study of small-scale coastal ocean processes and their coupling with atmospheric variability. In this presentation, we will analyze different data from recent glider campaigns in the southeast Bay of Biscay. Observations include sub-mesoscale processes such as coastal downwelling due to an intense storm and the exceptional extension of the Adour River plume to the east under the influence of northern winds.In October 2022, a glider mission covered a storm event, collecting data on temperature, salinity, current velocity, and acoustic information on pelagic fish and vertebrates. During the storm, western winds reached velocities up to 17 m/s, and surface currents ranged between 20 and 65 cm/s, partially oriented toward the coast. The glider's salinity and temperature profiles showed a downlift of isopycnals by approximately 20 m in the near-surface water masses at the shelf-break. After the storm, the temperature and salinity profiles gradually returned to their initial state after five days. In November 2023, a second glider mission revisited the area and measured temperature, salinity, turbidity, chlorophyll-a (Chl-a), dissolved oxygen (DO), colored dissolved organic matter (CDOM), and nitrates. The glider monitored the Adour River plume with high spatiotemporal resolution. During the mission and under norther winds, maximum surface currents measured by the HF radar reached 74 cm/s, promoting the westward extension of the river plume, visible in satellite SST and Chl-a maps.Better understanding the mechanisms of rapid coupling between atmospheric and oceanic processes in the coastal zone is vital for improving the prediction of currents, hydrographic conditions, and their effect on surface transport, or water mass exchanges, or biogeochemical cycles.

The Basque Meteorology Agency (Euskalmet) and the Directorate of Emergency Attention and Meteorology (DAEM), within the Department of Security of the Basque Government, are responsible for issuing warnings, alerts, and alarms in response to potential risk impacts. Euskalmet's mission includes the continuous forecasting and monitoring of severe weather situations, operating 24/7. Among the various risks considered, maritime-coastal risk is one of the most significant in the region, often leading to considerable economic losses. The impact on the coastline may worsen with rising sea levels and the increasing development of coastal areas if adequate measures are not taken. This contribution reviews the systems implemented in recent years for monitoring maritime-coastal risks and their integration into Euskalmet’s surveillance framework. Real-time monitoring plays a crucial role in the Basque maritime-coastal early warning system, which also integrates predictive models to enhance its forecasting capabilities. We provide an overview of the systems employed for real-time maritime-coastal risk monitoring, which convert raw data into actionable information. These systems focus on the three primary risks identified by the current operational framework: coastal wind reversals, navigation hazards, and coastal impacts. Additionally, continuous surveillance enables the detection of other meteorological hazards, such as low visibility and extreme winds, which also pose risks to the coastal zone. The data that powers these systems comes primarily from the Basque Ocean-Meteorological Observation Network, which includes a variety of observational instruments, such as coastal video cameras. A key feature of this monitoring system is the use of various panels in the prediction and surveillance room. These panels, displayed on a central video wall, allow on-duty staff to quickly assess the risks by monitoring several key parameters in real time. This paper also presents conclusions drawn from operational experience gained through monitoring maritime-coastal risk events in recent years. Continuous vigilance and real-time data analysis are essential for issuing early warnings and supporting decision-making processes for effective risk management.

Accurate ocean state forecasting is fundamental for effective port operations and coastal zone management. In the southeastern Bay of Biscay, particularly Pasaia port, high-resolution ocean condition forecasts directly impact navigation safety, port logistics, and environmental monitoring capabilities. The integration of observational data with numerical models represents a critical advancement in improving forecast accuracy for operational oceanography applications.This study addresses the challenge of enhancing ocean model performance through a systematic approach to data assimilation. We focus on incorporating high-frequency (HF) radar observations into the Iberian-Biscay-Irish (IBI) regional model framework to optimize boundary conditions of the MOHID model that is available in the area. The motivation stems from the need to reduce forecast uncertainties in coastal areas where complex bathymetry, tidal forcing, and meteorological conditions interact. By implementing a two-dimensional variational (2DVAR) assimilation scheme, we aim to minimize the discrepancies between model outputs and observational data, ultimately providing more reliable ocean state estimates for local maritime operations. To validate the improved model outputs, we will compare them against Lagrangian drifter trajectories using a skill score metric, ensuring the assimilation’s effectiveness in capturing complex ocean dynamics.

On December 8, 2023, the cargo ship Toconao was involved in a maritime incident off the coast of northern Portugal that resulted in the loss of 1,000 bags of buoyant plastic pellets, or nurdles. The pellets fell into the sea and reached the Bay of Biscay, posing a potential threat to the coasts of Spain and France. In the weeks following the incident, pellets were found washing up on beaches throughout northern Spain, particularly in Galicia, Asturias, Cantabria and the Basque Country. In response to this environmental emergency, several contingency plans were activated along the Spanish coast, requiring the use of scientific tools such as numerical modeling to develop effective responses. Nevertheless, a lack of detailed knowledge of the factors governing the transport and dispersion of these pellets made accurate predictions difficult, posing a significant challenge to effective management and mitigation of the spill.For this reason, a set of laboratory experiments was conducted to study the dispersion of pellets under a range of hydrodynamic and wind conditions in two different physical settings. The behavior of the pellets collected from the Toconao spill, which showed a density of 900 kg/m³, was assessed in two different sections of a hydraulic flume (Z1 and Z2 zones) under different combinations of water level, current, and wind. Zone Z1, located within the flume itself (2 m x 0.35 m), exhibits a unidirectional flow pattern. In contrast, zone Z2, located in the expanded section of the flume (3 m x 1.5 m), shows three-dimensional asymmetric flow patterns. Hydrodynamic conditions were defined by combining one water level in each zone (30 and 40 cm in Z1 and Z2, respectively) and three flow rates (30, 40 and 50 l/s in both zones). In addition, the effect of four wind conditions was tested for the average flow rate of 40 l/s (in Z1: no wind, 0.5, 1.0, and 1.5 m/s; in Z2: no wind, 0.3, 0.7, and 1.1 m/s). The results provide valuable information on the effects of wind and ocean currents on the dispersion of a group of plastic pellets and demonstrate the importance of surface currents in this process. In addition, these findings provide a comprehensive database for validating numerical transport models, which will improve their predictive ability and usefulness in future emergencies.

Keywords: Glider, Biogeochemical status, Multiplatform observations, Coastal Monitoring, Blue Economy Hub A 11-day glider mission was conducted in November 2023 in the SE Bay of Biscay. The glider was equipped with hydrographic and biogeochemical sensors, measuring temperature, salinity, turbidity, fluorescence, dissolved oxygen, CDOM, and nitrates. Additionally, it estimated integrated currents within the water column. These data were shared in real-time with the global Operational Oceanography community through collaboration with Coriolis DAC (Data Assembly Centre) and OceanOPS (WMO-IOC Support Center for in-situ observation programs of oceanography and marine meteorology). The monitored area encompassed the continental shelf and the upper slope of the Basque Country coast, which is covered by Copernicus Marine Service in-situ data from the EuskOOS observatory (https://euskoos.eus/mapv2/), including a HF radar and one slope buoy. In this work, we show the physical and biogeochemical variability related to a marked river plume event at an unprecedented spatio-temporal resolution, emphasizing the potential of combining in-situ, remote, and model data for effective coastal monitoring. During the mission, intense currents towards the W-SW favoured the westward extension of the Adour River plume, which resulted in low salinities and nitrate surface anomalies measured by the glider, coherent with the few available satellite data and model simulations from the Copernicus Marine System. This study is the first step for an enhanced observatory in the study area devoted to new services tailored for the coastal ocean user’s community, in the framework of the ongoing Oarsoaldea Blue Economy Hub initiative (https://www.azti.es/en/blue-economy-to-boost-oarsoaldea/).

Coastal upwelling has been extensively studied since it plays a critical role in the connectivity between offshore waters and coastal ecosystems, which has impacts on water quality, fisheries, and aquaculture production. Significant efforts have been devoted to the quantification of the intensity, duration, and variability of this phenomenon by means of coastal upwelling indexes (CUIs), derived from wind, sea level pressure, or sea surface temperature data. Although valuable, first-order descriptors, such classical indexes have been reported to present some limitations. As one of the major shortcomings is the omission of the direct influence of ocean circulation, this work introduces a novel CUI, generated from remotely sensed hourly surface current observations provided by a high-frequency radar (HFR). The consistency of the proposed index (CUI-HFR) is assessed in two different oceanographic areas during two distinct time periods: in the north-western Iberian (NWI) peninsula for 2021 and in the Bay of Biscay (BOB) for 2014. To this aim, CUI-HFR is compared against a traditional CUI based on hourly wind observations (CUI-WIND) provided by two buoys. Likewise, the skill of CUI-HFR to identify upwelling and downwelling processes is also qualitatively evaluated. Complementarily, the prognostic capabilities of the GLOBAL analysis and forecasting system to accurately reproduce upwelling and downwelling events in the NWI area are also analysed (CUI-GLOBAL). Results obtained in these two pilot areas revealed the following: (i) noticeable agreement between CUI-HFR and CUI-WIND, with correlation coefficients above 0.67; and (ii) a proven ability of CUI-HFR and CUI-GLOBAL to categorize a variety of upwelling and downwelling episodes, which highlights their potential applicability for direct upwelling monitoring over any coastal area of the global ocean.